Radio frequency magnetic field units, such as volume coils, are used in connection with imaging and/or spectroscopy systems, such as but not limited to magnetic resonance imaging systems, nuclear magnetic resonance imaging systems, functional magnetic resonance imaging systems, and electron spin resonance systems.
A problem with many cylindrical form volume coils is that they provide limited access to the coil volume. These cylindrical form volume coils can be accessed only through the ends of the cylinders or between the radio frequency (RF) current carrying rungs or loops. The “between the rung” or lateral access is further limited when the coil is shielded. A Faraday shield on a birdcage for example, completely screens the lateral walls of the coil cylinder with typically a copper clad, etched circuit board material. The result is a “copper can.” Similarly, the transverse electromagnetic (TEM) coil circuits are composed of a cylindrical symmetrical array of conductor rungs in parallel resonance with and enclosed by a copper resonant cavity. The limited access provided by end access or “between the rung” access to the coil volume affects a subject confined to the coil volume and physicians or technicians treating or interacting with the subject. Some subjects are claustrophobic and cannot tolerate confinement in a volume coil, while some medical procedures, such as brain surgery, require access to the subject during imaging. For these and other reasons there is a need for the present invention.